Statewide sampling of highway runoff continued through 1980-81, and the resulting data has been aggregated with that from previous years to further investigate pollutant loadings. Results have validated the solids loading model previously proposed by Asplund (1980) for Western Washington Highways and tentatively extended the model to Eastern Washington. Loading of other pollutants can be predicted from total suspended solids loading using ratios derived from the data. These ratios may be taken as constants at any Washington State location for some pollutants or as linear functions of traffic for other contaminants. Comparison of runoff from a sulfur-extended asphalt pavement with runoff elsewhere indicates higher sulfate loads in the former case. A limited sampling program along an uncurbed highway section observed higher pollutant concentrations from these sections to curbed areas. Sampling of solids adhering to the undercarriage of automobiles produced widely varying results but suggested that vehicles traveling on rural or unpaved roads accumulate significant amounts of solids that can be released on highways. The final year of field sampling will concentrate on improving the loading models, especially for Eastern Washington application, and continuing the sulfur-extended asphalt study with a functional control site experiencing the same conditions.